Check valves, mixer tap, different pressures

[reg091]

Fitting a new kitchen and mixer tap. HW is pumped at 2.4 Bar, CW is mains at 1.3 Bar.

I am thinking that the only "danger" of contamination is of the higher pressure HW forcing back into the cold supply via the mixer tap. Is that right?

In which case it seems I would only need a single check valve on the cold. Is that right?

I am loathe to fit a check valve on the cold as the the pressure is so low but if I have to then I have to.

 

[Newboy]

Most kitchen taps don't mix hot and cold in the valve body - the two supplies are kept separate to the end of the spout.

As long as you choose the correct tap there's no need for backflow prevention.

 

[reg091]

Thanks. Doesn't look like the one we got keeps the supplies separate. Looking up the spout there is only one hole that the water comes out of.

The spec doesn't say:

https://www.tapsuk.com/astini-colon...e-ceramic-handle-kitchen-sink-mixer-tap-p7842

 

[Madrab]

Most kitchen taps don't mix hot and cold in the valve body - the two supplies are kept separate to the end of the spout

Unfortunately I have to disagree, there are probably many more single flow kitchen taps than there are dual flow these days, it's simply down to cost. It's cheaper to make a single piece spout than a pipe within a pipe dual flow spout. Most monobloc kitchen taps will be single flow.

edit for shocking grammer

 

[Madrab]

@reg091, it's not just about contamination but also about getting a balanced supply. If one supply has a higher pressure than the other, it may restrict the lower supply therefore may be difficult to get the temperatures right. A Pressure Reducing Valve may also be needed which is pretty counter productive.

Why is the whole house HW pumped as it would always cause issue like this in the long run.

 

[reg091]

@reg091, it's not just about contamination but also about getting a balanced supply. If one supply has a higher pressure than the other, it may restrict the lower supply therefore may be difficult to get the temperatures right. A Pressure Reducing Valve may also be needed which is pretty counter productive.

Why is the whole house HW pumped as it would always cause issue like this in the long run.

The whole house is pumped (HW and CW) so pressures are equal at the bathrooms mixer taps, and showers. I guess it was done due to the low mains pressure and the hot water cylinder being on the ground floor (it was a a bungalow that has been extended into the loft).

The only mains fed (therefore drinkable) water is the kitchen tap.

The previous kitchen mixer tap seemed to mix water okay so I am keeping my fingers crossed that this one does. I have ordered a full-bore check valve for the cold.

 

[Hot&Cold]

Dualflow taps are available for unbalanced water supplies https://support.tapsuk.com/hc/en-us...ingle-flow-tap-and-what-is-and-dual-flow-tap-

 

[Madrab]

That makes sense then, I took from your OP that it was just the HW that was pumped.

As @Hot&Cold mentions there are dual flow taps available, just browse for them. The choice isn't as varied as single flow monoblocs are though.

 

[reg091]

Thanks guys. I wish I had done this research before buying the tap! However, it seems to be working fine (the missus is happy...) so I'll slap the check valve on the cold and leave it.